The present invention relates generally to elastomer-tipped metallic armatures and, more particularly, to an insert for use in an armature construction in which the length of the elastomer portion of the armature may be precisely controlled during the manufacture thereof.
Elastomer-tipped metallic armatures of various configurations are commonly used in electric solenoid assemblies used in fluid control applications. A typical armature is formed with a cylindrical metal body or insert which has a cavity or hole formed lengthwise in one end or which may extend through the entire length of the insert. An elastomer element is mounted within the hole and may extend beyond the end of the metal insert or it may have an end surface which is recessed behind the end surface of the insert. The elastomer tip formed at the end of the armature insert provides an effective means for forming a seal with another surface of the solenoid assembly to prevent fluid leaks, as well as forming a resilient contact surface for avoiding excessive wear between the sealing surfaces of the solenoid.
In many applications, the effectiveness of the solenoid assembly in operating in a leak-free manner depends on precisely controlling the length of the armature and, in particular, controlling the length of the elastomer element during the manufacture of the armature. The armature is conventionally formed by fabricating the metal insert, such that the length of the insert falls within certain specified tolerances and, subsequently, mounting the insert in a mold for molding and bonding the elastomer element in place within the insert. Finally, the elastomer element is ground down to place the overall armature length within the required tolerances for its application.
The armature construction described above suffers from the limitations imposed by the accuracy to which the elastomer grinding operation can be performed, which controls the tolerance limits within which the armature length can be maintained. In addition, if the armature design requires that the elastomer element be molded with the ends recessed from the ends of the metal insert, it may be difficult or impossible to grind the elastomer element down to the proper length dimensions.
Thus, there is a need to provide an armature construction by which the length of the armature of a solenoid assembly can be more precisely controlled and, in particular, there is a need for an armature construction in which the length of the elastomer element may be simply and precisely controlled.